JP2021150639A - Spin-orbit torque switching element with tungsten nitride - Google Patents

Abstract

To provide a SOT-MRAM that performs write operation at a low switching critical current.SOLUTION: A magnetic element 100 includes: a fixed layer 150 having a fixed magnetization direction; a free layer 130 having a magnetization direction to be switched; a tunnel insulation layer 140 located between the fixed layer and the free layer; and a spin torque generating layer 120 that injects a spin current Is into the free layer as an in-plane current Ic flows. The spin current switches the magnetization direction of the free layer by the spin-orbit torque. The fixed layer and the free layer have vertical magnetic anisotropy. The spin torque generating layer includes a tungsten layer 122 and a tungsten-nitride layer 124 which are sequentially laminated. The tungsten-nitride layer is placed adjacent to the free layer.SELECTED DRAWING: Figure 2

Description

The present invention relates to a spin-orbit torque (SOT) -based switching element, and more specifically, a tungsten layer / tungsten nitride capable of spin-orbit torque (SOT) switching at a low current. It relates to a spin-orbit torque (SOT) -based switching element including a material layer multilayer thin film.

The magnetic random access memory (MRAM) of the spin-orbit torque (SOT) switching board has a magnetic tunnel junction (MTJ) as a core element.

FIG. 1 shows a normal magnetic tunnel junction (MTJ).

As shown in FIG. 1, the magnetic tunnel junction 10 (MTJ) is composed of a spin torque generating layer / free layer / tunnel barrier layer / fixed layer.

The electrical resistance value of the tunneling current passing through the tunnel barrier layer 16 changes depending on the relative magnetization direction of the free layer 14 and the fixed layer 18. The magnetic tunnel junction 10 stores information by using such a tunnel magnetoresistive (TMR) phenomenon.

The magnetic tunnel junction 10 has vertical magnetic anisotropy (PMA) characteristics in order to achieve high tunnel magnetoresistance (TMR) ratio (TMO), high write stability, low write current, and high integration. Has. Vertical magnetic anisotropy means that the magnetization direction of the magnetic layer is perpendicular to the magnetic layer surface.

When an in-plane current Ic flows through the spin torque generating layer 12 adjacent to the free layer 14, the spin torque generating layer 12 has a spin Hall effect or a Rashba effect (spin Hall effect) or a Rashba effect (spin-orbit torque; SOT) due to the spin-orbit torque (SOT). Rashba effect) is used to induce free-layer switching. The spin-orbit torque writes information at a higher speed, lower current, and lower power consumption than the writing method of spin-transfer torque (STT).

However, in order to commercialize a spin-orbit torque (SOT) MRAM, a material and a structure of a spin torque generating layer capable of inducing magnetization reversal of the free layer by lower current injection are required.

An object to be solved by the present invention is to provide a SOT-MRAM that performs a write operation at a low switching critical current. When the spin torque generating layer that contacts the free layer and provides the in-plane current includes a multilayer thin film of a tungsten layer / tungsten nitride layer, the spin orbit torque effect of the SOT-MRAM is enhanced and the switching criticality for the write operation is enhanced. The current decreases. The tungsten nitride layer contains nitrogen-doped tungsten or tungsten nitride.

The problem to be solved by the present invention is that when a tungsten layer / tungsten nitride layer structure is used as the spin hole generation layer, vertical magnetic anisotropy is exhibited at a predetermined thickness and a predetermined nitrogen concentration of the tungsten nitride layer. It is to provide SOT-MRAM.

An object to be solved by the present invention is to provide a SOT-MRAM that operates even in a harsh environment of low temperature and high temperature, and then operates normally even after returning to room temperature.

An object to be solved by the present invention is to provide a SOT-MRAM having a low critical current and performing a magnetic field-free switching operation.

The magnetic element according to the embodiment of the present invention includes a fixed layer having a fixed magnetization direction, a free layer having a switching magnetization direction, and a tunnel insulating layer interposed between the fixed layer and the free layer. A spin torque generating layer that injects a spin current into the free layer as an in-plane current flows. The spin current switches the magnetization direction of the free layer by the spin-orbit torque. The fixed layer and the free layer have vertical magnetic anisotropy, and the spin torque generating layer includes a tungsten layer and a tungsten-nitride layer which are sequentially laminated. The tungsten-nitride layer is arranged adjacent to the free layer.

In one embodiment of the present invention, the tungsten-nitride layer has a thickness of 0.2 nm, and the tungsten nitride layer has an atomic percentage of nitrogen of 5% to 42%.

In one embodiment of the present invention, the atomic percentage of nitrogen in the tungsten nitride layer is 2% to 29%, and the thickness of the tungsten-nitride layer is 0.2 nm to 0.8 nm. be.

In one embodiment of the present invention, the atomic percentage of nitrogen in the tungsten nitride layer is 2% to 5%, and the thickness of the tungsten-nitride layer is 0.2 nm to 3 nm.

In one embodiment of the invention, the tungsten-nitride layer comprises a crystalline W ₂ N (111) phase, or the tungsten-nitride layer is a crystalline W ₂ N (111) phase and crystalline. Includes WN (100) phase.

In one embodiment of the invention, the tungsten layer is aligned perpendicular to the free layer.

In one embodiment of the present invention, the spin torque generating layer further includes a ferromagnetic layer having in-plane magnetic anisotropy, and the tungsten layer is arranged between the ferromagnetic layer and the tungsten nitride layer. Will be done.

In one embodiment of the present invention, the specific resistance of the tungsten-nitride layer is 350 μΩ · cm or more.

The magnetic element according to the embodiment of the present invention includes a fixed layer having a fixed magnetization direction, a free layer having a switching magnetization direction, and a tunnel insulating layer interposed between the fixed layer and the free layer. Includes a spin torque generating layer that injects a spin current into the free layer as an in-plane current flows, and a tungsten nitride layer arranged between the free layer and the spin torque generating layer. The spin current switches the magnetization direction of the free layer by the spin-orbit torque. The fixed layer and the free layer have vertical magnetic anisotropy, the spin torque generating layer includes a tungsten layer, and the tungsten-nitride layer is vertically aligned with the free layer.

The magnetic element according to the embodiment of the present invention includes a fixed layer having a fixed magnetization direction, a free layer having a magnetization direction to be itched, and a tunnel insulating layer interposed between the fixed layer and the free layer. A spin torque generating layer that injects a spin current into the free layer as an in-plane current flows. The spin current switches the magnetization direction of the free layer by the spin-orbit torque. The fixed layer and the free layer have vertical magnetic anisotropy, the spin torque generating layer includes a tungsten-nitride layer, and the atomic percentage of nitrogen in the tungsten-nitride layer is 2. % To 5%, the tungsten-nitride layer is arranged adjacent to the free layer.

According to an embodiment of the present invention, a SOT switching device using a multilayer structure of a tungsten layer / a tungsten nitride layer operates with a lower write current than a device using a conventional single tungsten layer.

According to the embodiment of the present invention, when the spin torque generating layer in contact with the free layer and providing the in-plane current includes the tungsten layer / tungsten nitride layer, the spin orbit torque effect of the SOT-MRAM is enhanced and the writing is performed. Switching critical current for operation is reduced.

According to the embodiment of the present invention, the SOT-MRAM operates even in a harsh environment of low temperature and high temperature, and then operates normally even after returning to room temperature.

According to an embodiment of the present invention, the multilayer structure of the in-plane magnetized ferromagnetic layer tungsten layer / tungsten nitride layer provides a SOT-MRAM having a low critical current and performing a magnetic field-free switching operation.

A normal magnetic tunnel junction (MTJ) is shown. It is sectional drawing which shows the magnetic element by one Example of this invention. It is a drawing which shows the magnetic element by one Example of this invention. FIG. 3A is a cross-sectional view of FIG. 3A. It is a magnetic element for measuring the SOT switching behavior according to one embodiment of the present invention. Atomic percent nitrogen tungsten nitride layer due to the flow rate Q of the _{N 2} gas in accordance with an embodiment of the present invention (nitrogen atomic percent) shown. _{The effective anisotropic energies Ku} and eff associated with the atomic percent n (nitrogen atomic percentage) of nitrogen in the tungsten nitride layer according to one embodiment of the present invention are shown. Effective anisotropy energy K _u due to the thickness t _W-N of the tungsten nitride layer according to an embodiment of the present _invention, the _eff shown. _{The absolute value | ξ DL} | of the spin Hall angle associated with the atomic percent n of nitrogen according to one embodiment of the present invention is shown. The absolute value of the spin Hall angle due to the thickness t _W-N of the tungsten nitride layer according to an embodiment of the present invention | xi] _{DL |} shown. The resistance associated with the conditional current of n at _{t W-N = 0.2 nm is shown.} The switching current associated with the conditional external magnetic field of n at _{t W-N = 0.2 nm is shown.} It shows the normalized switching current and vertical magnetic anisotropy associated with n at tW _{-N = 0.2 nm.} The normalized switching current and vertical magnetic anisotropy from n = 29% to n are shown. _{The resistivity ρ xx} (resistivity) is shown as a function of n in the structure of W (5 nm) / WN _x (t _{W−N =} 0.2 nm) / CoFeB (0.9 nm) / MgO (1 nm) / Ta (2 nm). The GIXRD (Glazing Incidence X-ray Diffraction) result of the tungsten nitride layer having a thickness of 40 nm is shown. The specific resistance of the tungsten nitride layer having a thickness of 40 nm is shown as a function of n. When n = 5%, the in-plane TEM images and the selected selected area diffraction (SAD) pattern are shown. When n = 34%, it indicates an in-plane TEM images and a selected area diffraction (SAD) pattern. When n = 42%, it indicates an in-plane TEM images and a selected area diffraction (SAD) pattern. It shows resistance associated with in-plane current at various temperatures under an external magnetic field Hex of +200 Oe. It shows the switching current associated with the external magnetic field at various temperatures. _{Nitrogen content n and WN x} layer in the _{W (5 nm) / WN x} (t _W-N ; n) / CoFeB (0.9 nm) / MgO (1 nm) / Ta (2 nm) structure according to one embodiment of the present invention. The experimental results according to the thickness are shown. It is sectional drawing which shows the magnetic element by another Example of this invention. It is sectional drawing which shows the magnetic element by another Example of this invention.

In the non-magnetic layer NM / ferromagnetic layer FM structure, the magnetization of the ferromagnetic layer NM is reversed by the spin orbital torque (SOT) generated when the in-plane current is injected into the non-magnetic layer NM. The SOT-switching board memory or logic device provides the advantages of reduced energy consumption and fast switching over conventional spin-transfer-torque-switched devices. However, two major obstacles must be resolved for commercialization. That is, deterministic switching and a very low switching current are required in the absence of an external magnetic field.

Spin-orbit torque (SOT) is used to reverse the magnetization of a ferromagnetic layer in a non-magnetic layer NM / ferromagnetic layer FM structure by injecting an in-plane current. Spin-orbit torque has attracted considerable interest as a new mechanism for magnetic random access memory. Among various heavy metals, β-phase tungsten membrane shows relatively high SOT efficiency. Therefore, the β-phase tungsten film is considered as a potential material for the spin current generation layer.

According to one embodiment of the invention, we report improved SOT and lower SOT-induced switching currents in _{the W / WN x / CoFeB / MgO Hall bar structure.} The CoFeB layer was perpendicularly magnetized. The WN layer is sputter-deposited in a nitrogen reactive environment. The composition of the WN _x layer affects the microstructure and electrical properties. The measured SOT efficiency is 0.54 and the switching current is reduced by about 1/5 in the sample containing 40% to 42% nitrogen atom percent than in the sample without the WN layer.

According to one embodiment of the invention, the W / WN / CoFeB / MgO structure provides a low switching current. When the in-plane magnetized ferromagnetic layer is placed below the tungsten layer, magnetic field switching is achieved.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the examples described herein, and may be embodied in different forms. Rather, the examples presented herein are provided so that the disclosed content is thorough and complete, and that the ideas of the present invention are fully communicated to those skilled in the art. In the drawings, the components are exaggerated for accuracy. Throughout the specification, the same elements are represented by the same reference number.

FIG. 2 is a cross-sectional view showing a magnetic element according to an embodiment of the present invention.

As shown in FIG. 2, the magnetic element 100 is interposed between the fixed layer 150 having a fixed magnetization direction, the free layer 130 having a switching magnetization direction, and the fixed layer and the fixed layer. It includes a tunnel insulating layer 140 and a spin torque generating layer 120 that injects a spin current into the free layer when the in-plane current Ic flows. The spin current switches the magnetization direction of the free layer 130 by the spin-orbit torque. The fixed layer 150 and the free layer 130 have vertical magnetic anisotropy. The spin torque generating layer 120 includes a tungsten layer 122 and a tungsten-nitride layer 124 which are sequentially laminated. The tungsten-nitride layer 124 is arranged adjacent to the free layer 130. The magnetic element 100 is a SOT-MRAM. The fixed layer 150, the tunnel insulating layer 140, and the free layer 130 form a magnetic tunnel junction.

The fixed layer 150 includes a ferromagnetic layer having a fixed magnetization direction and having vertical magnetic anisotropy. The fixed layer 150 has a single layer structure or a multi-layer structure.

The free layer 130 has vertical magnetic anisotropy and switches the magnetization direction by SOT. The free layer 130 is CoFeB having a thickness of 0.9 nm. The free layer 130 is transformed into a single-layer structure or a multi-layer structure.

The tunnel insulating layer 140 is MgO having a thickness of 1 nm as an insulator through which a tunnel current flows. The tunnel insulating layer 140 is arranged between the fixed layer 150 and the free layer 130.

The spin torque generating layer 120 contains a non-magnetic conductive metal. The spin torque generating layer 120 includes a tungsten layer 122 and a tungsten-nitride layer 124 which are sequentially laminated. When the in-plane current Ic flows through the spin torque generating layer 120, the spin torque generating layer 120 provides the spin current Is in the direction perpendicular to the arrangement plane (free layer direction). The spin current Is is SOT-generated by the Spin Hall effect (SHE) or the Spin Hall effect (SHE). The SOT switches the magnetization of the free layer 130. Both ends of the spin torque generating layer 120 are connected to an external circuit that applies an in-plane current via the connection electrodes 120a and 120b.

The switching current changes according to the thickness and composition of the tungsten-nitride layer 124. Further, the magnetization characteristics of the free layer are changed according to the thickness and composition of the tungsten-nitride layer 124. That is, the thickness and composition of the tungsten-nitride layer 124 provides perpendicular anisotropy to the free layer 130 within a predetermined range. When the free layer 140 exhibits vertical magnetic anisotropy, the thickness of the tungsten-nitride layer 124 decreases, and the switching current decreases as the nitrogen concentration increases.

Specifically, the thickness of the tungsten-nitride layer 124 is 0.2 nm, and the atomic percentage of nitrogen in the tungsten-nitride layer 124 is 5% to 42%. In this case, the free layer 130 maintains the vertical magnetic anisotropy, and the switching current decreases as the atomic percentage of nitrogen increases. On the other hand, when the atomic percentage of nitrogen exceeds 42%, the free layer 130 has in-plane magnetic anisotropy due to the disappearance of vertical magnetic anisotropy.

The atomic percentage of nitrogen in the tungsten-nitride layer 124 is 2% to 29%, and the thickness of the tungsten-nitride layer 124 is 0.2 nm to 0.8 nm. In this case, the free layer 130 maintains vertical magnetic anisotropy.

In the tungsten-nitride layer 124, the atomic percentage of nitrogen is 2% to 5%, and the thickness of the tungsten-nitride layer is 0.2 nm to 3 nm. In this case, the free layer 130 maintains vertical magnetic anisotropy.

The tungsten-nitride layer 124 contains a crystalline W ₂ N (111) phase (phase), or the tungsten-nitride layer 124 contains a crystalline W ₂ N (111) phase and a crystalline WN (100). ) Including phase. In this case, the free layer 130 maintains vertical magnetic anisotropy.

The electrode 160 is arranged on the fixed layer 150 and connected to an external circuit.

FIG. 3A is a drawing showing a magnetic element according to an embodiment of the present invention.

FIG. 3B is a cross-sectional view of FIG. 3A.

As shown in FIGS. 3A and 3B, the magnetic element 200 includes a free layer 130 having a switching magnetization direction, a tunnel insulating layer 140 arranged below the free layer, and the free layer as an in-plane current flows. Includes a spin torque generating layer 120 that injects a spin current into the magnet. The fixed layer and the free layer 130 have vertical magnetic anisotropy, and the spin torque generating layer 120 includes a tungsten layer 122 and a tungsten-nitride layer 124 which are sequentially laminated. The tungsten-nitride layer 124 is arranged adjacent to the free layer 130. The capping layer 162 is arranged on the tunnel insulating layer 140 and protects the tunnel insulating layer 140. The capping layer 162 is tantalum.

と

の２つの成分として表現される。

SOT is generated by the Spin Hall effect (SHE) of the non-magnetic layer NM or the spin torque generating layer or the Rashba-Edelstein effect of the non-magnetic layer NM / ferromagnetic layer FM interface. In the non-magnetic layer NM / ferromagnetic layer FM structure, the direction perpendicular to the non-magnetic layer NM / ferromagnetic layer FM interface is the z direction, and the in-plane current Ic is injected into the non-magnetic layer NM along the x direction. And, due to these two effects, spins in the y direction are accumulated. In this case, the torque generated by SOT is as follows.

When

It is expressed as two components of.

Here, τ _DL is damping-like (DL) -SOT. τ _FL is field-like (DL) -SOT. It is controversial as to what SOT has a dominant effect on magnetization reversal. However, an object of the present invention is to increase the size of the SOT and reduce the switching current.

The ratio of the spin current density J _{S to the in-plane current density J C} defined by the efficiency of SOT is called the spin Hall angle (SHA, ξ _SH = J _S / J _C ). As the spin Hall angle ξ _SH increases, a lower switching current is required to reverse the magnetization. In the case of heavy metal, _{it is known that the spin Hall angle ξ SH} is large, and the spin Hall angle ξ _SH is ~ 0.33 for tungsten W, ~ 0.15 for tantalum Ta, and ~ 0 for platinum Pt. It is a level of .10.

According to one embodiment of the present invention, the tungsten nitride layer 124 was inserted between the non-magnetic layer NM and the ferromagnetic layer FM in order to reduce the switching current, and the thickness and composition of the tungsten nitride layer 124 were controlled. .. Accordingly, the spin Hall angle ξ _SH increases to 0.54. Also, the current-induced SOT switching behavior is reduced to about 1/5 of the value without the tungsten nitride layer 124. Even with a very thin tungsten nitride layer 124 (thickness 0.2 nm), the SOT switching behavior changes depending on the nitrogen atom N content.

According to one embodiment of the present invention, _two layers of SiO having a thickness of 300 nm are vapor-deposited on a Si100 wafer. W / WN _x / CoFeB / MgO / Ta layers are sequentially laminated on the SiO _{2 layer.} The tungsten layer 122 and the tungsten-nitride layer 124 are deposited by a DC magnetron sputtering system.

The DC magnetron sputtering system was used for metal deposition in an initial vacuum of ^{5x10-9 Torr.} The working pressure is 1.3 mTorr in an Ar gas atmosphere. The tungsten nitride layer 124 was deposited by reactive sputtering. The ratio of injected Ar and N ₂ gas was controlled at a constant working pressure. The DC power density is fixed at ^{2.5 W / cm 2.}

RF magnetron sputtering system ^was used to deposit the tunnel insulating layer 140 in the initial vacuum and operating pressure 6mTorr of ^5x10 -9 Torr. The tunnel insulating layer 130 is MgO. The RF power density is fixed at ^{1.6 W / cm 2.}

The laminated structure of the magnetic element is Si / SiO ₂ / W (5 nm) / WN _{x (tW-N} ) / CoFeB (0.9 nm) / MgO (1 nm) / Ta (2 nm). The thickness _{t W-N} of the tungsten nitride layer 124 is 0 to change to 3 nm, the composition of tungsten nitride layer 124 was adjusted by changing to 50% 0 to the Q. Here, Q is the ratio Q = [N ₂ ] / [Ar + N ₂ ] of the N ₂ gas flow rate [N ₂ ] to the total gas flow rate [Ar + N _{2] during sputtering.}

The free layer 130 is CoFeB (0.9 nm). After the deposition of the capping layer 162, all samples were annealed in a furnace at 300 degrees Celsius for 1 hour at ^{10-6 Torr.} The capping layer 162 operates as a protective layer.

After annealing, the magnetic properties were measured at room temperature using a vibrating sample magnetometer (VSM). For measuring electrical properties, devices with a Hall bar structure 5 μm wide and 35 μm long are manufactured using photolithography. SOT efficiency is measured using harmonics measurement. During the measurement, the injected alternating current AC and frequency f were fixed at 1 mA and 13.7 Hz, respectively.

FIG. 4 is a magnetic element for measuring SOT switching behavior according to an embodiment of the present invention.

As shown in FIG. 4, in order to determine the SOT switching behavior, a dot-shaped pattern having a diameter of 4 μm is formed by anisotropic etching of the capping layer 162, the tunnel insulating layer 140, and the free layer 130 in order in a hole bar structure. Will be done. Switching characteristics are measured using a probe station. _{A pulse current I pulse} with a pulse width of 10 μs was applied to the device in the x-direction, and an external magnetic field _Hex was applied in the x-axis direction for crystalline switching. The magnetic element 200a has a hole bar structure and has a dot-shaped free layer 130, a tunnel insulating layer 140, and a capping layer 162.

The resistance of the tungsten nitride layer 124 was measured using a four-point probe. Rutherford backscattering (RBS) analysis was performed to confirm the composition of the tungsten nitride layer 124. The microstructure of the tungsten nitride layer 124 was analyzed using a passing X-ray diffraction device at a fixed angle of 0.5 degrees. The microstructure of the tungsten nitride layer 124 was observed using a transmission electron microscope.

Figure 5 illustrates an atomic percent of nitrogen in the tungsten nitride layer due to the flow rate Q of the _{N 2} gas in accordance with an embodiment of the present invention (nitrogen atomic percent).

As shown in FIG. 5, Q is the ratio Q = [N ₂ ] / [Ar + N ₂ ] of the N ₂ gas flow rate [N _{2 ] to the total gas flow rate [Ar + N 2] during sputtering.} The atomic percentage of nitrogen atoms in the tungsten nitride layer 124 was measured by a Rutherford backscattering device.

The nitrogen atom content of the tungsten nitride layer 124 was analyzed. The ratio Q of the N ₂ gas flow rate 0,4,8,15,20,30,40, and 50%. Atomic percent n of nitrogen is shown as a function of Q for a 40 nm thick tungsten nitride thin film examined using Rutherford Backscatter (RBS). At Q = 4%, the atomic percentage n of nitrogen is 5%, which is very small. At Q = 8%, the atomic percentage n of N increases sharply at 29%. Q = 20% and the atomic percentage n of nitrogen is 33%. However, between Q = 20% and Q = 30%, the atomic percentage n of nitrogen increases sharply again at 40%. With Q = 40%, the atomic percentage n of nitrogen is 42%.

_{FIG. 6 shows the effective anisotropic energy Ku} and eff associated with the atomic percent n (nitrogen atomic percentage) of nitrogen in the tungsten nitride layer according to an embodiment of the present invention.

As shown in FIG. 6, the magnetic element 200 has a W / (5 nm) / WN _x (0.2 nm) / CoFeB (0.9 nm) / MgO (1 nm) / Ta (2 nm) structure. _{The effective anisotropic energies Ku and eff} associated with the atomic percent n (nitrogen atomic percentage) of nitrogen in the tungsten nitride layer 124 were analyzed. The atomic percentage n (nitrogen atomic percentage) of nitrogen in the tungsten nitride layer 124 was changed in the range of 0 to 42%. The effective anisotropic energies _{Ku and eff} decrease as n increases. _{When the thickness tW-N} of the tungsten nitride layer 124 was fixed at 0.2 nm, the perpendicular magnetic anisotropy PMA was generated in the range of 0% to a maximum of 42% of the atomic percent n of nitrogen. However, PMA did not occur when the atomic percentage n of nitrogen exceeded 42%. Effective anisotropy energy _{K u, eff} is, n = a 2.87Merg / cm ³ 0%, and decreased with n = 42% to 1.81Merg / cm ^3. Therefore, the intensity of PMA decreased as n increased. The effective anisotropic energies _{Ku and eff} were calculated using the areas of the in-plane and out-of-plane MH loops.

7, the effective anisotropy energy K _u due to the thickness t _W-N of the tungsten nitride layer according to an embodiment of the present _invention, the _eff shown.

As shown in FIG. 7, the magnetic element 200 has a W (5 nm) / WN _{x (tW-N} ) / CoFeB (0.9 nm) / MgO (1 nm) / Ta (2 nm) structure. It has changed the thickness _{t W-N} of the tungsten nitride layer 124 in the range of 0.2Nm～3nm.

If the thickness _{t W-N} of the tungsten nitride layer 124 is _{t W-N} ≧ 0.4nm, perpendicular magnetic anisotropy PMA was expressed only on n ≦ 29%. At n = 29%, when the thickness _tW-N of the tungsten nitride layer 124 was greater than 1 nm, the perpendicular magnetic anisotropy PMA disappeared.

_{When the thickness tW-N} of the tungsten nitride layer 124 exceeded 1.0 nm, the perpendicular magnetic anisotropy PMA disappeared regardless of n.

Since the perpendicular magnetic anisotropy PMA is essential for the high density magnetic random access memory MRAM, we irradiate the SOT with a structure having the thickness and composition of the tungsten nitride layer 124 within the range where the perpendicular anisotropy PMA appears. bottom. To irradiate the magnetic transport property (magneto-transport transportation), the magnetic element with the perpendicular magnetic anisotropy PMA was manufactured using photolithography in a holer structure 5 μm wide and 35 μm long.

を用いて表現される。 We measured the magnetic transport characteristics of PMA magnetic devices by the harmonic method widely used to evaluate SOT. When an AC current is injected into the magnetic element and the _{magnetization is in equilibrium under the external magnetic field Hex} , the first harmonic component has the polar angles θ and

Is expressed using.

ここで、Ｒ_ＡＨＥは異常ホール抵抗（ａｎｏｍａｌｏｕｓ Ｈａｌｌ ｒｅｓｉｓｔａｎｃｅ）を表し、Ｒ_ＰＨＥは平面ホール抵抗（ｐｌａｎａｒ Ｈａｌｌ ｒｅｓｉｓｔａｎｃｅ）を表す。熱電電圧（ｔｈｅｒｍｏｅｌｅｃｔｒｉｃ ｖｏｌｔａｇｅ）に関連する２次高調波成分（ｓｅｃｏｎｄ ｈａｒｍｏｎｉｃ ｃｏｍｐｏｎｅｎｔ；Ｒ_ｘｙ ^２ω）は次の通りである。 [Number 1]

Here, R _AHE represents anomalous Hall resistance, and R _PHE represents a planar Hall response. The second harmonic component (R _xy ^2ω ) related to the thermoelectric voltage is as follows.

[Number 2]

Here, I ₀ represents the amplitude of the AC current, α represents the abnormal Nernst effect coefficient, and ∇ T represents the thermal contribution due to Joule heating.

_BI = B _DL + B _FL + _BOe represents the sum of the current-induced field. Here, B _DL is a damping-like field, B _FL is a field-like field, and _BOe is an Oersted field. B _DL and B _FL are effective magnetic fields generated by DL-SOT and FL-SOT, respectively. Magnetization oscillates in the direction of the effective magnetic field.

In the in-plane magnetization state θ = π / 2, DL-SOT and FL-SOT induce the magnetization to oscillate vertically and horizontally in a plane, respectively. Formula 2 is recreated as follows.
[Number 3]

の時に消滅する。このような仮定の下で、数式３はＤＬ−ＳＯＴによる有効フィールドである、Ｂ_ＤＬを計算するために近似化する。その次にＢ_ＦＬ＋Ｂ_Ｏｅが得られる。
［数４］

When the anisotropy field _{H K} sufficiently larger than the external magnetic field _{B ext} is applied, if the magnetization is in the plane of the film, the contribution of the resistance due to thermal gradients (thermal gradient) can be assumed to be constant. The second term of the planar Hall effect is

It disappears at the time of. Under these assumptions, Equation 3 is approximated to calculate _{B DL} , which is a valid field by DL-SOT. Then B _FL + _BOe is obtained.
[Number 4]

Then we can calculate the SOT efficiency. The spin Hall angle (Spin Hall Angle, ξ) is as follows.
[Number 5]

Here, e is represent electromagnetic charge, h represents the Planck's constant, M _S represents the saturation magnetization of the free layer, t _FM denotes the thickness of the free layer, J _e represents current density.

To obtain the spin Hall angle ξ _DL , we performed harmonic measurements by varying the direction of the _{external magnetic field Best.} We apply an external magnetic field _{B ext} twice greater than about 13-18kOe anisotropy field _{H K} of the magnetic element.

Since it is known that the FL-SOT efficiency of tungsten is about 10 times smaller than the DL-SOT efficiency, only the _{spin Hall angle ξ DL by DL-SOT is considered in the present invention.}

_{FIG. 8 shows the absolute value | ξ DL} | of the spin Hall angle associated with the atomic percentage n of nitrogen according to an embodiment of the present invention.

9, the absolute value of the spin Hall angle due to the thickness t _W-N of the tungsten nitride layer according to an embodiment of the present invention | xi] _{DL |} shows a.

As shown in FIGS. 8 and 9, | ξ _DL | gradually increases as n increases, reaching a maximum of 0.54 at n = 40%. The angle of this spin hole is much larger than that of tungsten alone. When n> 40%, | ξ _DL | decreases slightly.

In the W (5 nm) / CoFeB / MgO structure (n = 0%, t _{W-N =} 0 nm), the 5 nm thick W thin film is expected to be β-phase W, and the absolute value of the spin Hall angle | ξ _DL | Is 0.32 ± 0.02.

With a structure of W (5 nm) / WN _x (t _W-N ) / CoFeB (0.9 nm) / MgO (1 nm) / Ta (2 nm), | ξ _{DL | is t W-N under} the condition of n = 29%. It changes depending on. | ξ _DL | is _{slightly higher at tW−N =} 0.2 nm than without the tungsten nitride layer 124. However, at a thickness of the tungsten nitride layer 124 greater than 0.2 nm, | ξ _DL | gradually decreases as _{tW-N increases.} This result shows that the very thin tungsten nitride layer 124 can improve the SOT characteristics.

However, _{when tW-N} exceeds 0.2 nm, the properties of bulk tungsten nitride gradually appear and the SOT efficiency is lower than without the tungsten nitride layer 124. Nevertheless, _{when tW-N} exceeds 0.2 nm, the critical current for switching decreases.

FIG. 10 shows the resistance associated with the conditional current of n at tW _{-N = 0.2 nm.}

As shown in FIG. 10, when an external magnetic field _Hex = + 200Oe is applied to the magnetic element 200a in the x-axis direction, decisive switching of the free layer 130 occurs regardless of n.

The switching current I _SW decreases as n increases, and the switching direction remains constant counterclockwise as n changes.

In the W / CoFeB / MgO structure (n = 0%) without the tungsten nitride layer 124, the switching current I _SW is 8.58 ± 0.08 mA and the switching current density J _SW is 33.0 MAcm ² ). .. The switching current I _SW gradually decreases as n increases, from n = 40% to 1.49 ± 0.16 mA, which is 5 times smaller than the structure without the tungsten nitride layer 124.

FIG. 11 shows the switching current associated with the conditional external magnetic field of n at tW _{-N = 0.2 nm.}

As shown in FIG. 11, the dependence of the external magnetic field of the switching operation is displayed. At all nitrogen contents n, the switching current I _SW tends to decrease _{as the external magnetic field Hex increases.} When the external magnetic field _Hex direction is changed from + x to −x, the switching direction is changed clockwise, but the switching current I _SW is maintained substantially the same. This result confirms that good current-induced SOT switching operation occurs. Also, when the tungsten nitride layer 124 is applied to the SOT-MRAM, it reduces power consumption.

Next, the decrease in the switching current I _SW is due to the increase in _{| ξ DL |.} The switching current I _sw ^SO by SOT is expressed as follows.
[Number 6]

Here, A _NM represents the thickness of the nonmagnetic layer current is injected (or spin hole generating layer), H _{K, eff} represents the anisotropy field. t _FM is the thickness of the free layer. M _S is the saturation magnetization of the free layer. _Hex is an external magnetic field.

In Equation _{6, H ex} is smaller than _{H K,} the _{eff, M S H K, eff} / 2 is valid anisotropy energy _{K u,} may be ignored because it is the same as _eff. Therefore, when t _FM and _ANG are fixed, the switching current I _sw ^SO by SOT is directly proportional to the effective anisotropic energies _{Ku and eff.}

Since the insertion of the tungsten nitride layer 124 affects the degradation of Ku _{and eff , we investigate the possibility that the switching current I SW} is affected by the reduction of the effective anisotropic energy _{Ku and eff.}

FIG. 12 shows the normalized switching current and vertical magnetic anisotropy associated with n at tW _{-N = 0.2 nm.}

FIG. 13 shows the normalized switching current and vertical magnetic anisotropy associated with n at n = 29%.

As shown in FIGS. 12 and 13, as a function of n and _{t W-N,} respectively _{I SW} and _{K u,} a normalized value of _eff.

As shown in FIG. 12, the switching current I _SW and the effective anisotropic energies _{Ku and eff} decrease as n increases, but the rate of decrease is considerably different. Starting at n = 34%, the switching current I _SW begins to decrease more rapidly than the effective anisotropic energies _{Ku and eff} , and this difference increases as n increases.

Again, as shown in FIG. 9, _| ξ _DL | decreases as the thickness t _W-N of the tungsten nitride layer 124 is increased. Nevertheless, as shown in FIG. 13, it decreases as the thickness t _W-N of the switching current I _SW of the tungsten nitride layer 124 is increased.

_However, a decrease in _{I SW} as _{t W-N} is changed is different from the case of increasing the _n, there is substantially the same tendency as _{K u,} the ratio of _eff. Therefore, ISW decreases _{as tW -N} increases due to changes _{in Ku and eff} rather than improvement in SOT efficiency. This result indicates that significantly affected SOT efficiency and _{K u} with improved reduction of _{I SW} due to the increase of _n, by reducing the _eff. Insertion of a very thin tungsten nitride layer 124 improves SOT switching efficiency. Therefore, the thin tungsten nitride layer 124, which has an atomic percent n of nitrogen of about 40%, offers considerable advantages in terms of power consumption of the SOT-MRAM.

We discuss how the configuration of the tungsten nitride layer 124 inserted in the FM / NM interface affects SOT efficiency. One possible cause of the improved efficiency is a change in electrical resistance due to the presence of impurities. Spin Hall effect Intrinsic and side-jump scattering, which is a possible cause of SHE, is associated with the _{resistivity ρ xx of the material.}

Impurities in the material can increase _{scattering and ρ xx} values and improve _{ξ SH. We measure ρ xx} with a Hall bar element and prove that _{the improvement in | ξ DL | is due to the increase in ρ xx} as n increases in the W-N layer.

FIG. 14 shows a W (5 nm) / WN _x (t _{W−N =} 0.2 nm) / CoFeB (0.9 nm) / MgO (1 nm) / Ta (2 nm) structure with a specific resistance ρ _xx (resistivity) as a function of n. ) Is shown.

As shown in FIG. 14, ρ _xx is represented by a function of n at t _{W−N = 0.2 nm.} The ρ _xx value is almost constant at most n values, but increases rapidly at n = 40%. At n = 40%, | ξ _DL | is the maximum. This result indicates that _{the effect of resistance on ξ DL} cannot be ignored, but ξ _DL was not exactly proportional to the resistance of the W / WN _{x / CoFeB / MgO structure.} Therefore, it is interpreted that factors other than resistance affect SOT efficiency.

Another possible cause is the effect of the microstructure of the tungsten nitride layer 124, such as crystallinity or phase. To confirm this assumption, we observed microstructural changes in the W film as n increased.

However, it is very difficult to analyze the microstructural changes of the ultra-thin tungsten nitride layer with a thickness of 0.2 nm. Therefore, we analyzed a tungsten nitride film with a thickness of about 40 nm and hypothesized that such changes would also occur in the ultrathin layer.

FIG. 15 shows the GIXRD (Glazing Incidence X-ray Diffraction) result of a tungsten nitride layer having a thickness of 40 nm.

As shown in FIG. 15, if the _{N 2} gas is injected into the sputtering (n = 0%), W peak clearly expressed in 2 [Theta] = 40 degrees near. Here, the 5 nm-thick W film we used for the SOT measurement is the β-W phase (phase), and the 40 nm-thick WN _x film is the α-W phase (phase). On a 40 nm thick WN _x film, after n increases to 5%, the W (110) peak decreases sharply, the line width widens, and the peak moves to the left and approaches the _{W 2 N peak.} This result indicates that as n increases, W ₂ N begins to form and the crystallinity of W decreases.

Next, as n further increases, the line width of the peak further widens, and the peak gradually moves to the left _{and almost coincides with the W 2} N (111) peak at n = 34%. This, n is eliminated almost W-phase exceeds 30%, indicating that only nanocrystalline W _{2 N} thin film exists.

When n exceeds 40%, the peak moves further to the left and approaches the WN (100) peak, and at n = 42%, the peak becomes more vivid and the crystallinity is improved. This result is consistent with the WN binary phase diagram.

As the nitrogen atom content increases, the steps appear in the order _{W → W + W 2} N → W ₂ N → W _{2 N + WN.} Here, W ₂ N appears at about n = 34%. The phase iagram is in close agreement with the experimental results.

Next, the resistivity of the tungsten nitride film was measured and compared with that reported in previous studies.

FIG. 16 illustrates the specific resistance of a tungsten nitride layer having a thickness of 40 nm as a function of n.

As shown in FIG. 16, the dotted line indicates the boundary of the tungsten nitride phase change predicted by the XRD analysis. The resistivity of the tungsten nitride layer is maintained at 200-260 μΩ · cm until n = 29%, but rapidly increases to 350 μΩ · cm or more at n> 30%.

When n exceeds 40%, the specific resistance rapidly increases again to 500 μΩ · cm or more. The resistance of the sputtered tungsten nitride layer is highly dependent on deposition conditions such as pressure, sputtering power and temperature. However, in general, as the ratio Q of the N ₂ gas flow rate [N ₂ ] to the total gas flow rate [Ar + N ₂ ] increases, the specific resistance increases. Also, as the crystallinity increases, the non-resistance decreases. This is consistent with the results of our experiments.

Experimental results show that after the resistivity increases to n = 40%, the resistivity decreases slightly as the determinacy increases at n = 42%.

Besides XRD analysis, we also look like nanocrystals because the peak intensity was too low to stably index the phase using XRD, so we used TEM to make a 40 nm thick tungsten nitride. Analyze the layers.

FIG. 17 shows in-plane TEM images and selected area diffraction (SAD) patterns when n = 5%.

As shown in FIG. 17, when n = 5%, polycrystalline grains appear in the nanocrystalline matrix.

When n = 5%, the SAD pattern indicates that W and W ₂ N coexist. The inner dotted circle represents the W ₂ N (111) grain. W ₂ N (111) grains is identified by applying a mask to the index has been (indexed) ring pattern _W 2 N (111) a fast Fourier transform image.

Polycrystalline Glenn (Polycrystalline grains) is _{W 2} N, indicating that the W film when the nitrogen is injected is almost nanocrystals (nanocrystalline).

FIG. 18 shows in-plane TEM images and selected area diffraction (SAD) patterns when n = 34%.

As shown in FIG. 18, TEM and SAD image with distinct ring pattern indicates that only nanocrystalline _W 2 N (111) is present at n = 34%.

FIG. 19 shows in-plane TEM images and selected area diffraction (SAD) patterns when n = 42%.

As shown in FIG. 19, when n = 42%, other grains are formed in the nanocrystalline matrix. WN (100) appears in the SAD pattern. Therefore, the results of XRD and TEM are in agreement, and it is confirmed that the phase of _{the WN x thin film depends on n.}

To find the cause of the improved SOT effect, we investigated the effect of n on the insertion of the tungsten nitride layer.

As shown in FIGS. 14 and 16, the specific resistance ρ _xx value of the magnetic element and the specific resistance of the tungsten nitride film having a thickness of 40 nm are slightly different. _{However, the specific resistance ρ xx} value of the magnetic element and the specific resistance of the tungsten nitride film having a thickness of 40 nm both show the maximum values at n = 40%.

In the magnetic element of FIG. 14, the tungsten nitride layer having a thickness of 0.2 nm is very thin compared to the total thickness of other films. Therefore, the influence of the 0.2 nm thick tungsten nitride layer on the resistivity is not dominant.

Also, although it is difficult to apply microstructure analysis to ultrathin films with perfect accuracy, the value of n is expected to affect the microstructure of the tungsten nitride layer.

Microstructural changes, such as changes in phase and crystallinity, are accompanied by changes in resistivity. Therefore, the resistivity and the fine structure are not considered separately.

Adjusting the nitrogen content of the tungsten nitride layer increases _{| ξ DL} | and decreases _{I SW.} However, additional research is needed on the physical origin of the improved SOT switching behavior that relies on the tungsten nitride layer.

To confirm the suitability of the W / WN _x (t _{W-N =} 0.4 nm) / CoFeB / MgO structure for MRAM applications, we discuss the stability of the magnetic device temperature at low and high temperatures.

To determine the temperature dependence of the switching current, tests were performed on devices with tW _{-N = 0.4 nm and n = 29%, which change the temperature in the following order.}
(1) Room temperature (RT) → (2) -100 ° C → (3) RT → (4) + 100 ° C → (5) RT.

FIG. 20 shows the resistance associated with the in-plane current at various temperatures under an external magnetic field _{Hex of +200 Oe.}

As shown in FIG. 20, switching by SOT works well counterclockwise at all temperatures.

FIG. 21 shows switching currents associated with an external magnetic field at various temperatures.

As shown in FIG. 21, when the temperature decreases from (1) room temperature (RT) to (2) -100 ° C, the switching current increases. When the temperature increases to + (4) 100 ° C. at (3) room temperature (RT), the switching current decreases. It is widely known that the SOT-induced switching current decreases at higher temperatures than at lower temperatures due to thermal fluctuations. However, the switching current is maintained constant in (1) the initial room temperature state, (3) the room temperature state after cooling, and (5) the room temperature state after heating. These results confirm that the device can operate in poor environments at various temperatures and operate normally without changing the operating current even after experiencing low and high temperature environments. Therefore, this means that _{the structure using the WN x} layer is suitable for SOT-MRAM application.

We investigated the improvement of SOT and the decrease of SOT-induced switching current by interface engineering of _{W / WN x} / CoFeB / MgO structure having a tungsten nitride layer. When the nitrogen content of the tensten nitride layer increased to 40%, we observed a high SOT efficiency of 0.54 and a decrease in switching current at about 1/5 of the value of the W / CoFeB / MgO structure.

The microstructure of films with varying nitrogen contents was analyzed through XRD and TEM. Results, SOT improve not only the specific resistance depends on the composition of the Tensuten nitride layer, it has found that caused by the microstructure changes (when tungsten is changed on W _{2 N} and WN).

_{FIG. 22 shows the nitrogen content n in the W (5 nm) / WN x (tW-N} ; n) / CoFeB (0.9 nm) / MgO (1 nm) / Ta (2 nm) structure according to an embodiment of the present invention. The experimental results according to the thickness of the _{WN x layer are shown.}

As shown in FIG. 22, PMA represents vertical magnetic anisotropy and IMA represents in-plane anisotropy. The _{atomic percentage of the WN x} layer is 2% to 29%, and the thickness of the WN layer is 0.2 nm to 0.8 nm. In this case, the free layer (CoFeB (0.9 nm) maintains vertical magnetic anisotropy.

The atomic percentage of nitrogen in the WN _x layer is 2% to 5%, and _{the thickness of the WN x} layer is 0.2 nm to 3 nm. In this case, the above (CoFeB (0.9 nm) maintains vertical magnetic anisotropy.

Whether the WN _x layer comprises crystalline _W 2 N (111) phase, or, the WN _x layer comprises crystalline _W 2 N (111) phase and crystalline WN (100) phase. In this case, the free layer (CoFeB (0.9 nm) maintains vertical magnetic anisotropy.

On the other hand, in _{the case of a magnetic device having no tungsten layer and only a WN x} layer of 5 nm, the free layer exhibits vertical magnetic anisotropy only when the nitrogen content n is 2% to 5%.

FIG. 23 is a cross-sectional view showing a magnetic element according to another embodiment of the present invention.

As shown in FIG. 23, the magnetic element 300 is interposed between the fixed layer 150 having a fixed magnetization direction, the free layer 130 having a switching magnetization direction, and the fixed layer and the free layer. A tunnel insulating layer 140, a spin torque generating layer 320 that injects a spin current into the free layer as an in-plane current flows, and a tungsten-nitriding layer 324 arranged between the free layer and the spin torque generating layer. And, including. The spin current switches the magnetization direction of the free layer 130 by the spin-orbit torque. The fixed layer 150 and the free layer 130 have vertical magnetic anisotropy, the spin torque generating layer 320 includes a tungsten layer, and the tungsten-nitride layer 324 is vertically aligned with the free layer. NS.

The switching current is changed according to the thickness and composition of the tungsten-nitride layer 324. Further, the magnetization characteristics of the free layer are changed according to the thickness and composition of the tungsten-nitride layer 324. That is, the thickness and composition of the tungsten-nitride layer 324 provides perpendicular anisotropy to the free layer 130 within a predetermined range. When the free layer 140 exhibits vertical magnetic anisotropy, the thickness of the tungsten-nitride layer 324 decreases, and the switching current decreases as the nitrogen concentration increases.

Specifically, the thickness of the tungsten-nitride layer 324 is 0.2 nm, and the atomic percentage of nitrogen in the tungsten-nitride layer 324 is 5% to 42%. In this case, the free layer 130 maintains the vertical magnetic anisotropy, and the switching current decreases as the atomic percentage of nitrogen increases. On the other hand, when the atomic percentage of nitrogen exceeds 42%, the free layer 130 loses its vertical magnetic anisotropy and has an in-plane magnetic anisotropy.

The atomic percentage of nitrogen in the tungsten-nitride layer 324 is 2% to 29%, and the thickness of the tungsten-nitride layer 324 is 0.2 nm to 0.8 nm. In this case, the free layer 130 maintains vertical magnetic anisotropy.

The atomic percentage of nitrogen in the tungsten-nitride layer 324 is 2% to 5%, and the thickness of the tungsten-nitride layer is 0.2 nm to 3 nm. In this case, the free layer 130 maintains vertical magnetic anisotropy.

The tungsten-nitride layer 324 contains a crystalline W ₂ N (111) phase (phase), or the tungsten-nitride layer 324 has a crystalline W ₂ N (111) phase and a crystalline WN (100) phase. including. In this case, the free layer 130 maintains vertical magnetic anisotropy.

Both ends of the spin torque generating layer 320 are connected to an external circuit that applies an in-plane current.

FIG. 24 is a cross-sectional view showing a magnetic element according to another embodiment of the present invention.

As shown in FIG. 24, the magnetic element (400) is interposed between the fixed layer 150 having a fixed magnetization direction, the free layer 130 having a switching magnetization direction, and the fixed layer and the free layer. The tunnel insulating layer 140 is included, and the spin torque generating layer 420 that injects a spin current into the free layer as an in-plane current flows. The spin current switches the magnetization direction of the free layer 130 by the spin-orbit torque. The fixed layer 150 and the free layer 130 have vertical magnetic anisotropy, and the spin torque generating layer 420 includes a tungsten layer 122 and a tungsten-nitride layer 124 which are sequentially laminated. The tungsten-nitride layer 124 is arranged adjacent to the free layer 130.

The spin torque generating layer 420 further includes a ferromagnetic layer 421 having in-plane magnetic anisotropy. The tungsten layer 122 is arranged between the ferromagnetic layer 421 and the tungsten-nitride layer 124. The magnetization direction of the ferromagnetic layer 421 is parallel or antiparallel to the direction in which the in-plane current flows. An interface-generated spin current is generated between the ferromagnetic layer and the tungsten layer. The interface-generated spin current has spin polarization of the z-axis component. Accordingly, spin-orbit torque switching can be realized without an in-plane magnetic field.

Both ends of the spin torque generating layer 420 are connected to an external circuit that applies an in-plane current via the connection electrodes 120a and 120b.

Although the present invention has been illustrated and described with respect to specific preferred examples, the present invention is not limited to such examples, and a person having ordinary knowledge in the technical field to which the invention belongs is within the scope of claims. It includes all examples of various forms that can be carried out without departing from the claimed technical idea of the present invention.

100: Magnetic element 120: Spin torque generating layer 122: Tungsten layer 124: Tungsten-nitride layer 130: Free layer 140: Tunnel insulating layer 150: Fixed layer

Claims (10)

A fixed layer with a fixed magnetization direction and
A free layer with a switching magnetization direction and
A tunnel insulating layer interposed between the fixed layer and the free layer,
A spin torque generating layer, which injects a spin current into the free layer as an in-plane current flows, is included.
The spin current switches the magnetization direction of the free layer by the spin-orbit torque.
The fixed layer and the free layer have vertical magnetic anisotropy and have vertical magnetic anisotropy.
The spin torque generating layer includes a tungsten layer and a tungsten-nitride layer which are sequentially laminated.
The tungsten-nitride layer is a magnetic element characterized in that it is arranged adjacent to the free layer. The thickness of the tungsten-nitride layer is 0.2 nm.
The magnetic device according to claim 1, wherein the tungsten nitride layer has an atomic percentage of nitrogen of 5% to 42%. The atomic percentage of nitrogen in the tungsten nitride layer is 2% to 29%.
The magnetic element according to claim 1, wherein the thickness of the tungsten-nitride layer is 0.2 nm to 0.8 nm. The atomic percentage of nitrogen in the tungsten nitride layer is 2% to 5%.
The magnetic element according to claim 1, wherein the tungsten-nitride layer has a thickness of 0.2 nm to 3 nm. The tungsten - or nitride layer comprises a crystalline _W 2 N (111) phase, or,
The tungsten - nitride layer, the magnetic element according to claim 1, characterized in that it comprises a crystalline W _{2 N} (111) phase and crystalline WN (100) phase. The magnetic element according to claim 1, wherein the tungsten layer is vertically aligned with the free layer. The spin torque generating layer further includes a ferromagnetic layer having in-plane magnetic anisotropy.
The magnetic element according to claim 1, wherein the tungsten layer is arranged between the ferromagnetic layer and the tungsten nitride layer. The magnetic element according to claim 1, wherein the specific resistance of the tungsten-nitride layer is 350 μΩ · cm or more. A fixed layer with a fixed magnetization direction and
A free layer with a switching magnetization direction and
A tunnel insulating layer interposed between the fixed layer and the free layer,
A spin torque generating layer that injects a spin current into the free layer as an in-plane current flows,
Includes a tungsten nitride layer disposed between the free layer and the spin torque generating layer.
The spin current switches the magnetization direction of the free layer by the spin-orbit torque.
The fixed layer and the free layer have vertical magnetic anisotropy and have vertical magnetic anisotropy.
The spin torque generating layer includes a tungsten layer, and the spin torque generating layer includes a tungsten layer.
A magnetic element in which the tungsten-nitride layer is vertically aligned with the free layer. A fixed layer with a fixed magnetization direction and
A free layer with a switching magnetization direction and
A tunnel insulating layer interposed between the fixed layer and the free layer,
A spin torque generating layer, which injects a spin current into the free layer as an in-plane current flows, is included.
The spin current switches the magnetization direction of the free layer by the spin-orbit torque.
The fixed layer and the free layer have vertical magnetic anisotropy and have vertical magnetic anisotropy.
The spin torque generating layer includes a tungsten-nitride layer and contains.
The atomic percentage of nitrogen in the tungsten-nitride layer is 2% to 5%.
The tungsten-nitride layer is a magnetic element characterized in that it is arranged adjacent to the free layer.

Images